Cell-penetrating peptides (CPPs) can be peptides of less than 30 amino acids that may be able to penetrate cell membranes and translocate different cargo into cells. The mechanism of cell translocation can be receptor and energy independent. Although, in certain cases, translocation can be partially mediated by endocytosis.
The cell membrane can pose a hurdle to the use of pharmacologically active biomacromolecules that are not per se actively translocated into cells. One approach to deliver such molecules involves tethering or complexing them with CPPs that are able to cross the plasma membrane of cells.